Three journalists were detained by the Tamil Nadu Police while covering the black flag protest against the Chennai-Salem Green Express Highway project in Thiruvannamalai district on Tuesday.

Mathrubhumi TV reporter K Anoop Das, cameraman Murugan and car driver Razak along with CPM mouthpiece Theekkathir’s reporter-cum-cameraman S Ramadoss were taken into custody by district police at the CPM office.

The journalists claimed that they were detained by the police despite being told that they were scribes and had come only to cover the protests.

Das claimed that the police manhandled him and refused to let him go even after he showed his press identity card.

They were let off only after a video sent by Das about the incident went viral on social media.

Superintended of Police R Ponni said that the journalists were detained when they were searching for some other accused there.

"They were let go once their identity was established," she said.

Black flag protests were held in all five districts — Salem, Dharmapuri, Krishnagiri, Thiruvannamalai and Kancheepuram  — against the Rs 10,000 crore project which would require thousands of acres of farm lands.